Highly Efficient Yolk–Shell Photocatalyst Constructed by Integration of Ni₂P and Cu₂O Nanoparticles to Defective Metal–Organic Frameworks for Visible-Light-Driven Amine Oxidation

Realizing the directional migration of photogenerated carriers plays an important role in improving the photocatalytic performance. Meanwhile, light-driven oxidative coupling of benzylamine under ambient conditions with an inexpensive catalyst is highly desirable for the industrial field. Herein, via in situ synthesis, defect engineering, and photodeposition, a yolk–shell nanostructured photocatalyst, Ni₂P@OH-NH₂–UiO-66@Cu₂O, featuring nickel phosphide (Ni₂P) nanoparticles (NPs) trapped inside a defect engineered metal–organic framework (MOF, namely OH-NH₂–UiO-66) and Cu₂O NPs adhering on the surface of MOFs, has been rationally fabricated for the achievement of spatial separation of oxidation/reduction cocatalyst in photocatalytic reaction systems. The yolk–shell structure can effectively avoid the aggregation of the Ni₂P and Cu₂O NPs. Remarkably, the separation of electron collector Ni₂P and hole collector Cu₂O regulates the directional movement of the photogenerated carriers and effectively improves the electron–hole separation efficiency to generate abundant reactive superoxide radicals (^•O₂^–) and hydroxyl radicals (^•OH). Ni₂P@OH-NH₂–UiO-66@Cu₂O achieves a conversion of 99% for the oxidative coupling of benzylamine into imine within 1 h at ambient temperature under visible-light irradiation. The present study provides an economical method to construct a MOF-based yolk–shell photocatalyst for the oxidative coupling of amines.